It does nothing to reduce the consumption frenzy, and it does nothing to remove CO2 / CH4 from the atmosphere, and it does nothing to reduce insolation.
Something like the MEER:ReflEction project[1] seems to be more appropriate to me.
It can cleanly (zero excess carbon) provide vast amounts of energy for direct air capture of CO2 (energy is the biggest barrier for that).
The efforts proposed in the site you linked require huge geological-scale engineering efforts never before attempted. Nuclear is really here and it works well the overwhelmingly vast majority of the time.
Don't get me wrong, changing mindsets and reducing consumptive behavior are at the root of the problem as well, just remember that 'perfect' is the enemy of 'good'.
It does nothing to reduce the consumption frenzy, and it does nothing to remove CO2 / CH4 from the atmosphere, and it does nothing to reduce insolation.
Something like the MEER:ReflEction project[1] seems to be more appropriate to me.
[1]: https://www.meerreflection.com/home